I did an upgrade from kernel 5.4.0-74-generic to 5.4.0-77-generic and the problem disappeared.
$ stty -F /dev/ttyACM0 speed 57600 baud; line = 0; eof = ^A; min = 1; time = 0; -brkint -icrnl -imaxbel -opost -onlcr -icanon -echo -echoe -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux-firmware in Ubuntu. https://bugs.launchpad.net/bugs/1931684 Title: cdc_acm: acm_port_activate - usb_submit_urb(ctrl irq) failed Status in intel-microcode package in Ubuntu: Confirmed Status in linux package in Ubuntu: Confirmed Status in linux-firmware package in Ubuntu: Confirmed Bug description: Ubuntu 18.04.5 LTS Recently, after kernel update 4.15.0.144 (didn't know about the case yet), i can't open serial ports on USB CDC devices (STM32 Virtual COMs in my case). using simple cat command (with or without sudo): $ sudo cat /dev/ttyACM1 cat: /dev/ttyACM1: Input/output error or some serial programs: Failed to connect to /dev/ttyACM1 : [Errno 5] could not open port /dev/ttyACM1: [Errno 5] Input/output error: '/dev/ttyACM1' dmesg: [ 3295.718270] cdc_acm 1-2:1.0: ttyACM1: USB ACM device [ 3302.508356] cdc_acm 1-2:1.0: acm_port_activate - usb_submit_urb(ctrl irq) failed [ 3302.508940] cdc_acm 1-2:1.0: acm_port_activate - usb_submit_urb(ctrl irq) failed When i try spamming commands while plugging the device in, i am sometimes able to open the port (might be the clue). When i booted in ubuntu advanced mode to 4.15.0.143 kernel, everything started to work normally. Also tried HWE stack with 5.4.0.74 kernel, but the bug was also present there. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/intel-microcode/+bug/1931684/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
